1. Field of the Invention
An apparatus consistent with the present invention relates to a servo writer for writing servo patterns on tape-shaped information recording media, such as magnetic tapes and optical tapes.
2. Description of the Related Art
Ever since magnetic tapes were applied to information recording media for computers, the recording density of magnetic tapes has been increased. To implement this high recording density, the linear recording technology is mainly employed. This linear recording technology is suitable for an information back-up use for computers in terms of the realization of a high data rate. A magnetic tape to which the linear recording technology is applied has multiple data bands thereon in the recording direction (e.g. along the long side of the tape), each data band being an area where information is to be recorded. Further, in this linear recording technology, multiple servo bands are also formed on the magnetic tape in the running direction prior to use. Each servo band is formed by writing multiple servo patterns on the magnetic tape, and these servo patterns are written by a servo writer.
A typical servo writer includes (a) a supply reel that feeds a magnetic tape, (b) a take-up reel that winds the magnetic tape, and (c) a magnetic head that writes servo patterns on the magnetic tape (see Japanese Unexamined Patent Application 2003-1418360). The servo writer uses the magnetic head to write servo patterns on a magnetic tape, while running the magnetic tape between the supply and take-up reels.
Furthermore, in order to record/reproduce information on or from magnetic tapes, a drive is used. Such a drive allows a recording/reproducing head to track the servo bands on a magnetic tape, while reading the servo patterns. Further, the recording/reproducing head records/reproduces information on or from the data bands between the adjacent servo bands, while tracking the servo bands. This enables positioning of the recording/reproducing head relative to the running magnetic tape (the data band) with great accuracy. As a result, the narrowing of the data bands and of the pitches between the adjacent data bands is achieved. In other words, high recording density magnetic tapes can be obtained.
A magnetic tape is formed by slitting a wide web into a predetermined width, and the edges of this tape are formed upon cutting. Referring to FIG. 5A that is a partially enlarged view depicting an edge portion of a magnetic tape, it is found that this tape edge is not always straight. If a magnetic tape MT having such a non-straight edge is operated by a drive, as shown in FIG. 5B, then it slightly displaced along the width while being led by a guide 42 of the drive.
Typically, a recording/reproducing head 41 of the drive manages to track servo bands SB under the control of a servo control mechanism 43 (actuator), even if the servo bands SB are slightly displaced. However, if a displacement amount W of the magnetic tape MT is excessively large, then it is difficult for the recording/reproducing head 41 to exactly trace the servo bands SB. In addition, it is expected that data bands and the pitches between adjacent data bands are increasingly narrowed to follow the recent trend toward the high recording density. Therefore, if the servo bands are not traced exactly, then the recording/reproducing head may be run them off, thus causing tracking errors.
Taking the above disadvantage into account, the present invention has been conceived. An object of the present invention is to provide a servo writer which forms servo bands on information recording media so as to enable a drive to track the servo bands with great accuracy by using a recording/reproducing head.